1 //===- llvm/Support/Memory.h - Memory Support -------------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file declares the llvm::sys::Memory class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_SUPPORT_MEMORY_H
15 #define LLVM_SUPPORT_MEMORY_H
17 #include "llvm/Support/DataTypes.h"
19 #include <system_error>
24 /// This class encapsulates the notion of a memory block which has an address
25 /// and a size. It is used by the Memory class (a friend) as the result of
26 /// various memory allocation operations.
28 /// @brief Memory block abstraction.
31 MemoryBlock() : Address(nullptr), Size(0) { }
32 MemoryBlock(void *addr, size_t size) : Address(addr), Size(size) { }
33 void *base() const { return Address; }
34 size_t size() const { return Size; }
37 void *Address; ///< Address of first byte of memory area
38 size_t Size; ///< Size, in bytes of the memory area
42 /// This class provides various memory handling functions that manipulate
43 /// MemoryBlock instances.
45 /// @brief An abstraction for memory operations.
48 enum ProtectionFlags {
54 /// This method allocates a block of memory that is suitable for loading
55 /// dynamically generated code (e.g. JIT). An attempt to allocate
56 /// \p NumBytes bytes of virtual memory is made.
57 /// \p NearBlock may point to an existing allocation in which case
58 /// an attempt is made to allocate more memory near the existing block.
59 /// The actual allocated address is not guaranteed to be near the requested
61 /// \p Flags is used to set the initial protection flags for the block
63 /// \p EC [out] returns an object describing any error that occurs.
65 /// This method may allocate more than the number of bytes requested. The
66 /// actual number of bytes allocated is indicated in the returned
69 /// The start of the allocated block must be aligned with the
70 /// system allocation granularity (64K on Windows, page size on Linux).
71 /// If the address following \p NearBlock is not so aligned, it will be
72 /// rounded up to the next allocation granularity boundary.
74 /// \r a non-null MemoryBlock if the function was successful,
75 /// otherwise a null MemoryBlock is with \p EC describing the error.
77 /// @brief Allocate mapped memory.
78 static MemoryBlock allocateMappedMemory(size_t NumBytes,
79 const MemoryBlock *const NearBlock,
83 /// This method releases a block of memory that was allocated with the
84 /// allocateMappedMemory method. It should not be used to release any
85 /// memory block allocated any other way.
86 /// \p Block describes the memory to be released.
88 /// \r error_success if the function was successful, or an error_code
89 /// describing the failure if an error occurred.
91 /// @brief Release mapped memory.
92 static std::error_code releaseMappedMemory(MemoryBlock &Block);
94 /// This method sets the protection flags for a block of memory to the
95 /// state specified by /p Flags. The behavior is not specified if the
96 /// memory was not allocated using the allocateMappedMemory method.
97 /// \p Block describes the memory block to be protected.
98 /// \p Flags specifies the new protection state to be assigned to the block.
99 /// \p ErrMsg [out] returns a string describing any error that occurred.
101 /// If \p Flags is MF_WRITE, the actual behavior varies
102 /// with the operating system (i.e. MF_READ | MF_WRITE on Windows) and the
103 /// target architecture (i.e. MF_WRITE -> MF_READ | MF_WRITE on i386).
105 /// \r error_success if the function was successful, or an error_code
106 /// describing the failure if an error occurred.
108 /// @brief Set memory protection state.
109 static std::error_code protectMappedMemory(const MemoryBlock &Block,
112 /// This method allocates a block of Read/Write/Execute memory that is
113 /// suitable for executing dynamically generated code (e.g. JIT). An
114 /// attempt to allocate \p NumBytes bytes of virtual memory is made.
115 /// \p NearBlock may point to an existing allocation in which case
116 /// an attempt is made to allocate more memory near the existing block.
118 /// On success, this returns a non-null memory block, otherwise it returns
119 /// a null memory block and fills in *ErrMsg.
121 /// @brief Allocate Read/Write/Execute memory.
122 static MemoryBlock AllocateRWX(size_t NumBytes,
123 const MemoryBlock *NearBlock,
124 std::string *ErrMsg = nullptr);
126 /// This method releases a block of Read/Write/Execute memory that was
127 /// allocated with the AllocateRWX method. It should not be used to
128 /// release any memory block allocated any other way.
130 /// On success, this returns false, otherwise it returns true and fills
132 /// @brief Release Read/Write/Execute memory.
133 static bool ReleaseRWX(MemoryBlock &block, std::string *ErrMsg = nullptr);
135 /// InvalidateInstructionCache - Before the JIT can run a block of code
136 /// that has been emitted it must invalidate the instruction cache on some
138 static void InvalidateInstructionCache(const void *Addr, size_t Len);
140 /// setExecutable - Before the JIT can run a block of code, it has to be
141 /// given read and executable privilege. Return true if it is already r-x
142 /// or the system is able to change its previlege.
143 static bool setExecutable(MemoryBlock &M, std::string *ErrMsg = nullptr);
145 /// setWritable - When adding to a block of code, the JIT may need
146 /// to mark a block of code as RW since the protections are on page
147 /// boundaries, and the JIT internal allocations are not page aligned.
148 static bool setWritable(MemoryBlock &M, std::string *ErrMsg = nullptr);
150 /// setRangeExecutable - Mark the page containing a range of addresses
152 static bool setRangeExecutable(const void *Addr, size_t Size);
154 /// setRangeWritable - Mark the page containing a range of addresses
156 static bool setRangeWritable(const void *Addr, size_t Size);
159 /// Owning version of MemoryBlock.
160 class OwningMemoryBlock {
162 OwningMemoryBlock() = default;
163 explicit OwningMemoryBlock(MemoryBlock M) : M(M) {}
164 OwningMemoryBlock(OwningMemoryBlock &&Other) {
166 Other.M = MemoryBlock();
168 OwningMemoryBlock& operator=(OwningMemoryBlock &&Other) {
170 Other.M = MemoryBlock();
173 ~OwningMemoryBlock() {
174 Memory::releaseMappedMemory(M);
176 void *base() const { return M.base(); }
177 size_t size() const { return M.size(); }
178 MemoryBlock getMemoryBlock() const { return M; }